There will be a science report in Dongfang Huge Plays Theatre on Sunday morning. Here is a notice to the audience.
       Notice to the audience
       Please bring your ticket. If you don't have your ticket, you can't go into the hall.  
       Don't run or shout in the hall. If you do, you'll have to leave.
       Don't wear slippers. If you do, the workers won't let you in.
       Keep your mobile phone off. If you don't, you will bother others.
       Please don't bring your under 12-year-old children here. If they come, I they won't understand the
report.
       Keep the hall clean. Don't throw your rubbish around. Or the hall will be dirty.
       Don't bring any food into the hall. If you do, the workers will take it away.
A: Are you free tomorrow?
B: Yes. Why?
A: Are you going to listen to   1  ?
B: Where?
A:   2   I have two tickets. Would you like to go with me?
B: Great, I'd love to. But I have to take my little nephew there.
A:   3   
B: What will happen   4  ?
A: He can't understand the report. He can't keep quiet.
B: Yes, you are right. Let's bring some food.
A: Oh, we can't do that. If we bring some food,  5  .
B: Oh, I see.

A. in; have to
B. at; must
C. in; must
D. at; have